With the right speakers, there is no reason to ever replace the Atma-sphere M60s, though I will hold on to my Music Reference RM10 MKIIs for as long as I listen to music. I thought my CAT JL2 was a keeper for life, and if they did not weigh 200lbs, I probably would have kept them, but their weight and heat got me into the Atma-spheres and when an OTL works with a speaker, I've not found anything better.